CD writes on geographical distribution – "a grand game of chess with the world for a board".

Gives his hypothetical explanation why zoology of Cape [of Good Hope] is not so peculiar as its botany: it was once a group of islands – later united.

Tries hard to set forth the difficulties of his [species] theory.

Tells CJFB in confidence of his theory of the glacial epoch and its effect on plant distribution, such as identical species being found on summits of mountains in the tropics. Invites him to attack his "doctrine".